Dr. Cecelia Brewington, diagnostic radiologist
and vice chair, UT Southwestern Medical
Center reviews a colonography scan.

CT trends from four angles

November 26, 2019
by John W. Mitchell, Senior Correspondent
While CT has been around a lot longer than other advanced imaging tools, the way it's utilized continues to change. Progress with reducing dose exposure, introducing sophisticated techniques, gaining coverage for life-saving exams, and improving interoperability are all currently taking place.

Here we take a quick look at a few news items that reflect the evolving state of CT.

Pregnancy CT scans on the rise
Pregnant women in Canada and the U.S. are being exposed to more radiation as they undergo an increasing rate of CT scans. A study published in JAMA Network Open found that in a 21-year review period, CT exams on pregnant women increased nearly fourfold in the U.S. and doubled in Ontario, Canada. HCB News checked back in with senior author and researcher Dr. Rebecca Smith-Bindman, a multispecialty professor, including radiology, biostatistics, and obstetrics, at the University of California, San Francisco, School of Medicine on the study.

“It is important for physicians to know not to recommend CT in pregnant women unless it is absolutely necessary," Smith-Bindman said. "Often, imaging can be deferred altogether, but if imaging is needed, tests such as ultrasound and MR that do not use ionizing radiation should be used whenever possible as first-line imaging.”

The researchers tracked data within the National Cancer Institute's Radiation-Induced Cancers study from six U.S. and Ontario-based healthcare systems for advanced imaging during the pregnancies of 2.2 million women who had 3.5 million live births in total between 1996 and 2016. Imaging modalities included radiation-emitting exams such as CT, radiography, angiography/fluoroscopy, and nuclear medicine, as well as MR scans that do not emit radiation.

While Smith-Bindman stressed that although technical improvements have made CT helpful across a broad range of diagnoses, patient demand and strong financial incentives have also contributed to the rise in utilization.

“We are studying the impact of CT in pregnant women in terms of future cancers in their children, and hope to have results to share within the next year or two,” she said.

New CT AI research spots tiny lung tumors with high accuracy
A research team at the University of Central Florida’s Computer Visions Research Center (UCFCVRC), using an AI platform dubbed S4ND, taught CT scanners to locate tiny tumors that would otherwise have been too small to find. The research utilized an approach similar to algorithms used in facial recognition software to scan thousands of faces for a particular pattern to find a match. The technique is modeled after the brain, where neuronal connections strengthen as it develops and learns.

“Radiologists may miss small tumors easily; this is the nature of the perceptual errors (bias) in radiology rooms," Dr. Ulas Bagci, principal investigator at UCFCVRC and lead researcher told HCB News. "Our lung cancer detection study is able to recover small tumors less than 3 mm. In clinical practice, some of these tumors may not be even undergoing biopsy, but they have to be controlled with follow up scans. If missed, that opportunity goes too."

Their work was first published in advance of last year’s Medical Imaging Computing & Computer Assisted Intervention conference. According to Bagci, the S4ND AI platform makes significant progress in reducing false positives often associated with AI research and currently has the highest tumor detection score of any known system.

"What is significant about S4ND, is the abandoning of multi-step, multi-stage, or multi-scale processing and the complete removal of any post-processing, while producing even higher accuracy detection results ... In short, it's much faster and more accurate," he added.

Bagci said that UCFCVRC has also developed a state-of-the-art AI diagnostic tool for early MR detection of pancreatic cystic tumors. He said that while there is still much work to do, his team believes it can significantly aid radiologists in tumor detection, speeding up read times and delivering an earlier diagnosis.

"Early detection is an important factor in survival rates of patients, and this is an area of radiology that we think AI can help significantly," said Bagci.

ACR pursues legislation to get Medicare coverage for CT virtual colonoscopy
One of the most significant barriers to new medical protocols is getting reimbursement approval from payers. It can be a fine line between what payers see as experimental versus what has been shown to have money saving benefits and provide better outcomes. Getting Medicare coverage for CT virtual colonoscopy, or colonography (CTC) has been an ongoing challenge along these lines.

Nearly 40 states require private insurers to cover virtual colonoscopy and any insurers who take part in federal exchanges under the ACA are also required to cover the exam. For screening advocates, the next step is coverage under Medicare.

A bipartisan bill has been introduced to Congress that would accomplish this and is currently in the House Ways and Means and Energy Commerce Committees, according to Shawn Farley, the director of public affair for the ACR. The bill, which is backed by the US Preventative Services Task Force, would give seniors the same coverage as the privately insured.

“At present, at least a third of those who should be screened for colorectal cancer are choosing not to get tested, contributing to a great many deaths each year,” Farley told HCB News. “Studies (in the U.S.) and abroad show virtual colonoscopy use dramatically increases screening rates.”

Unlike traditional colonoscopy, colonography does not require sedation. It is also less invasive and faster. In terms of accuracy, research in the New England Journal of Medicine has shown virtual colonoscopy is comparable to colonoscopy for average-risk patients. Studies also show that screening Medicare patients with virtual colonoscopy would cost nearly a third less than with colonoscopy. This would save up to $1.7 billion per screening cycle.

Opposition to virtual colonoscopy screening is based on a Congressional Budget Office (CBO) “score” that Medicare availability of CTC would increase utilization. However, CBO is barred from considering the significant downstream savings as a result of catching cancer early, such as the reduced need for chemotherapy and radiation therapy, according to Farley.

“This CBO score is a challenge to passage of Medicare coverage for CTC,” he said. “It is unlikely to pass as stand-alone legislation. The best chance for passage is as part of a larger healthcare bill.”

A call for standardizing CT calibration
Interoperability in healthcare has far-reaching implications. From patient information sharing to overhauling care delivery for a value-based paradigm, getting data out of silos and across competing technologies could be a boon for providers. The same concept also holds promise for comparing CT results across different OEM scanners with the use of a universal measurement method.

“It comes down to, what is the definition supposed to be?” Dr. Zachary Levine, a physicist at the National Institutes of Standards and Technology (NIST) told HCB News. In short, Levine said, a universal calibration measurement would mean less testing to verify pathology from clinical site to site, reducing costs and making it easier for the patient. The approach was originally reported in the journal PLOS ONE in March.

"One thing I notice is that within the CT's from any given vendor, there is high precision, i.e., high repeatability. But the comparison between vendors is much worse, suggesting low accuracy, meaning that the measurements do not have a common definition," he said. "We're still using standards that were fully appropriate in 1969, but the technology has improved and we can do better."

Levine said that since March, he has received several inquiries about imaging-based measurement standardization from his peers. This includes applying the idea for more accurate proton therapy results to avoid tumor surgeries.